Focusbar is a free Mac productivity tool that hopes to keep you on task with subtle reminders whenever you've switched windows. To use Focusbar, enter the one task that you'd like to work on, whether it's tackling email or working on slides for an upcoming presentation.

Should you stop doing your chosen activity and play on, say, Facebook, a small bar will pop up that shows the task you previously entered. For another Mac productivity tool that helps you fight multitasking, check out OneTask.

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